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'03 outback limited, '01 Outback Limited, '01 Legacy L wagon, '96 Legacy Brighton wagon
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Discussion Starter #1
Finally had my first longish drive today, in the cold ( 0 to 15 degrees) with a passenger. All good except:

Frigid cold air pouring on to my passengers feet! No matter what heat setting we tried, it still came in. Hot air is indeed blowing from the lower vent when sitting still - not sure about it when moving.

Before I go into the dash to see what is what (can't find a decent diagram of the system as yet), is there a separate vent for the cold air/ Going on the same trip again Thursday, but I don't have the time tomorrow to do much of any work on the car, so if something as simple as taping over a discharge vent will get rid of the problem for the duration of the trip, that is all it will get right now.

Suggestions?
 

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Lawn ornament XT
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14,366 Posts
Sediment obstruction in the heater core.

Hot coolant normally flows left to right through the heater core. When the heater loop gets restricted, the coolant moves too slowly. The blower is capable of extracting all the heat from the coolant before it has made it over to the right side.

Backflush the garbage out of the heater core and you should be good.
 

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'03 outback limited, '01 Outback Limited, '01 Legacy L wagon, '96 Legacy Brighton wagon
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Discussion Starter #3
Heat is fine everywhere else - quite toasty on the drivers side vents, as well as the passenger side dash vents. Would not the air be cold in all vents if the heater core was plugged/partially plugged? It is only that one vent that has frigid air coming out of it.
 

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2000 Outback Limited sedan 2.5 At,2001 Outback LL Bean 3.0 AT
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102 Posts
Mine only blows cold air when my setting was on fresh air.
 

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'03 outback limited, '01 Outback Limited, '01 Legacy L wagon, '96 Legacy Brighton wagon
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Discussion Starter #5
So nobody has any ideas about this cold air out of only one vent issue?
 

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03 H6 OBW & 06 WRX Sportwagon
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rasterman responded correctly based on some relatively recent info. There are multiple posts that point to noticebale differential temps L-to-R due to issues with the heater core.

hard for me to wrap my head around it too, but it seems legit.
 

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'03 outback limited, '01 Outback Limited, '01 Legacy L wagon, '96 Legacy Brighton wagon
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Discussion Starter #7
Hmmm.... Strange that that could be, since it is ONLY that one lower vent on the right side that gives the cold air, unless the output side of the core is immediately split left/right, but even that doesn't make much sense since only one outlet is affected. I guess that I'll have to just tape off that vent for tomorrows drive and dive into it deeper next week.
 

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Lawn ornament XT
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I probably can't explain it properly, but I'll have a go-

From what I've been able to work out, when the air is blown through the heater core and the discharge control is set to defrost, all the air out of the heater core meets and mixes in a common plenum before it goes out the dash rim vent. You get the hot-hot air from the left side of a blocked heater core mixed with the cold air from the right side, and the net effect is approximately normal defrost temp & action.

However, when you select the lower vents, there is no common mix plenum. Air that went through the left side of the heater core comes out the left side vents. Air that went through the right side of the core goes straight to the right side tubes. I don't think the lateral isolation was deliberate- I think they just didn't have enough space in there for a mixing chamber flowing in that direction.

My own car has started showing weaker heat on the right. I get to try it for myself before long. :)

I'm really hoping it is just a restriction in the heater core- that's a lot easier to fix than removing the dashboard and pulling apart the air box.
 
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